For the first time a phenomenon called light-by-light scattering has been observed, and is the first direct evidence of light interacting with itself at high energy. The observation took place at the Large Hadron Collider's (LHC) ATLAS detector in 2015 when lead nuclei were smashed together and, owing to the higher than normal energy used in the collision, a dense cloud of photons was involved. Light-by-light scattering was first described by the Euler-Heisenberg Lagrangian published in 1936 by Hans Heinrich Euler and Werner Heisenberg (of the uncertainty principle), and is impossible in classical theories of electromagnetism, but provides a sensitive test of our understanding of QED, the quantum theory of electromagnetism. The next run of the LHC is planned for the end of 2018, and holds the promise for a new field of study. To find out more check out ATLAS sees first direct evidence of light-by-light scattering at high energy.